Birth Control Light Period Pregnancy ?

Hello! I am on birth control and I take it like clockwork.

I had unprotected sex (no condom) for the first time earlier this month. My period came as expected but was much lighter than normal. I would only use one pad a day... that’s not my normal!

My period lasted 5 days and just ended. Now I’m getting post period cramps and my breasts feel heavy.

Has anyone had a fluke light period and cramping after a period?